Garcia has been a key force in Benfica's midfield since his €7 million move from Real Madrid in the summer of 2009.
Cadena Cope reports the 24-year-old's performances have now drawn the attention of the Italian and English champions who are both looking at the viability of a January deal for the player.
However, Garcia's agent, Manuel Garcia Quillon has denied the story.
"There is nothing," he told Antena 1.
"He is very happy at Benfica and he will stay at the club."
Man United boss Sir Alex Ferguson had a first hand look at the player's ability when Benfica clashed with his side almost a month ago.
Benfica held United to a 1-1 draw in their UEFA Champions League Group C encounter back in mid-September with Garcia playing the role of holding midfielder to perfection.